genetic code

genetic

[jĕ-net´ik]

1. pertaining to reproduction or to birth or origin.

2. inherited.

genetic code the arrangement of nucleotides in the polynucleotide chain of a chromosome; it governs the transmission of genetic information to proteins, i.e., determines the sequence of amino acids in the polypeptide chain making up each protein synthesized by the cell. Genetic information is coded in DNA by means of four bases: two purines (adenine and guanine) and two pyrimidines (thymine and cystosine). Each adjacent sequence of three bases (a codon) determines the insertion of a specific amino acid. In RNA, uracil replaces thymine.

genetic map

1. the location of mutations along the length of a chromosome, as determined by recombination experiments. The unit of length is the centimorgan (cM), one crossover per meiosis.

2. the sequence of base pairs along the DNA of a chromosome, a technique being applied to humans.

A gene map of Chromosome 18. From Copstead, 1996.

genetic marker a gene having alleles that are all expressed in the phenotype, that is, they are codominant, and which can be used to study inheritance. The various blood group systems and serum or red blood cell proteins easily detected by electrophoresis or immunodiffusion are commonly used markers.

ge·net·ic code

the genetic information carried by the specific DNA molecules of the chromosomes; specifically, the system whereby particular combinations of three consecutive nucleotides in a DNA molecule control the insertion of one particular amino acid in equivalent places in a protein molecule. The genetic code is almost universal throughout the prokaryotic, plant, and animal kingdoms. There are two known exceptions: In ciliated protozoans, the triplets AGA and AGG are read as termination signals instead of as l-arginine. This is also true of the human mitochondrial code, which, in addition, uses AUA as a code for l-methionine (instead of l-isoleucine) and UGA for l-tryptophan (instead of a termination signal).

genetic code

n.

1. The set of DNA and RNA sequences that determine the amino acid sequences used in the synthesis of an organism's proteins. It is the biochemical basis of heredity and nearly universal in all organisms.

2. The set of 64 codons corresponding to the 20 amino acids used for protein synthesis and as the signals for starting and stopping protein synthesis.

genetic coding n.

genetic code

the information carried by DNA that determines the specific amino acids and their sequence in each protein synthesized by an organism. The code consists of the sequence of nucleotides in the DNA molecule of each chromosome in the nucleus of every cell. During transcription, a specific part of the code is transcribed into a sequence of nucleotides in the messenger RNA (mRNA). The mRNA travels from the nucleus to the cytoplasm, where it is translated into protein by the ribosomes. A codon consisting of three consecutive nucleotides in the mRNA codes for each amino acid in the protein. A change in the code may result in an incorrect sequence of the amino acids in the protein, causing a mutation. See also anticodon,transcription,translation.

genetic code

Genetics A sequence of nucleotides, coded in triplets/codons along the mRNA, that determines the sequence of amino acids in a protein; a gene's DNA sequence can be used to predict an mRNA sequence; the 'words' and 'language' that govern the way in which genetic information–DNA is 'written' in the genome and translated into the proteins that perform the genes' activities. See Amino acid, Code, Codon, DNA, Gene, DNA sequence, Nucleotide, Protein, RNA.

ge·net·ic code

(jĕ-net'ik kōd)

The genetic information carried by the specific DNA molecules of the chromosomes; specifically, the system whereby particular combinations of three consecutive nucleotides in a DNA molecule control the insertion of one particular amino acid in equivalent places in a protein molecule.

genetic code

The sequence of the bases, adenine, guanine, cytosine and thymine, lying along the nucleic acid (DNA) molecules, the chromosomes. The bases occur in groups of three, each group being called a codon and each codon contains any three of the four in any order. This gives 64 different combinations, allowing some redundancy. A particular codon selects a particular one of the 20 amino acids or an instruction such as ‘gene starts here’ or ‘end of gene’. The sequence of codons ensures that a number of particular amino acids are linked together in a particular order so as to form a protein molecule-usually an ENZYME that promotes some biochemical process.

genetic code

a collection of CODONS of DNA and RNA that contains the information for synthesis of PROTEINS. Each codon is a triplet of BASES, derived from the four bases of the nucleic acid: A denine, C ytosine, G uanine and T hymine (or U racil in RNA), thus giving 43 = 64 combinations. The codons code for the AMINO ACIDS of the POLYPEPTIDE CHAIN, and also for the start (initiation) signals (commonly AUG, sometimes GUG) and the stop (termination) signals (UAG, UAA and UGA) in TRANSLATION. Note that the code shows DEGENERACY. Where there is more than one codon for a particular amino acid, certain organisms will preferentially utilize one codon rather than another to encode that amino acid, a phenomenon called CODON USAGE. The genetic code as shown in Fig. 169 is often referred to as being ‘universal’, with the same proteins being encoded by a particular base sequence in different organisms. However, there are exceptions, at least in some mitochondria, where certain codons code for different amino acids from those shown in the figure. For example, in mammalian mitochondria AGA and AGG function as the stop codons in translation.

code

1. a set of rules governing one's conduct. Called also ethical code.

2. a system by which information can be communicated.

3. a set of alphabetical or numerical markers which are an index to a much larger bank of information.

the arrangement of nucleotides in the polynucleotide chain of a chromosome that governs the transmission of genetic information to proteins, i.e. determines the sequence of amino acids in the polypeptide chain making up each protein synthesized by the cell. See also genetic code.

code of practice/conduct

a document produced by an authoritative body to provide a guide to people in their conduct relative to, for example, animal welfare, or their practice, for example, in the housing and feeding of pigs. It is the sort of document that is used when testing in a practical situation rules which are planned to be included in subsequent legislation.

genetic

1. pertaining to reproduction or to birth or origin.

2. inherited.

genetic abnormality

inherited defect, which may or may not be congenital.

genetic analysis

analysis of breeding and pedigree records to establish degrees of relationship between single animals and groups of animals. Segregation analysis with full-sibling families is an obvious technique.

genetic code

the manner in which the arrangement of nucleotides in the polynucleotide chain of a chromosome governs the transmission of genetic information to proteins, i.e. determines the sequence of amino acids in the polypeptide chain making up each protein synthesized by the cell. Genetic information is coded in DNA by means of four bases (two purines: adenine and guanine; and two pyrimidines: thymine and cystosine). Each adjacent sequence of three bases (a codon) determines which of the 20 amino acids will be inserted into the nascent polypeptide.

the manipulation of genes by recombinant DNA technologies to produce chromosomal combinations that are unlikely to occur by natural means, for example the introduction of genes for insulin into a yeast cell which then produces insulin which can be purified and used as a therapeutic substance. See also recombinant DNA technology.

genetic etiology

disease caused by inheritance of specific disease without the intervention of other risk factors; established by strongly positive relationship in terms of genes held in common between the affected patient and other affected individuals.

genetic evaluation

assessment, for predictive purposes, of productive improvement or conformational characteristics, of the gain to be derived by the use of the animal in question in a breeding program.

inherited productivity but still influenced by environmental risk factors.

genetic resistance

genetically determined resistance to specified infectious agents.

genetic selection

selection of animals as breeding stock on the basis of known inherited characteristics.

transposable genetic elements

pieces of DNA varying in length from a few hundred to tens of thousands of base pairs found in both prokaryotic and eukaryotic cells that move from place to place in the chromosomes of a single cell; some are viruses. Called also mobile genetic elements or transposons.

genetic variance

that portion of the phenotypic variance of a trait in a population which can be attributed to genetic difference amongst individuals.

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